Known frequency synthesizers generally comprise:    a first frequency-synthesizing stage capable of generating, at an output terminal, a signal s0(t) oscillating at a frequency f0, this first stage comprising a phase-locked loop,    a rendering terminal at which the signal st(t) oscillating at the frequency ft is rendered.
The drawback of known synthesizers, such as those comprising voltage-controlled oscillators (VCOs) feed-back controlled in a phase-locked loop is that their space requirement is often great.
Moreover, telecommunications systems often rely on the use of different carrier frequencies modulated by pieces of information to be transmitted. Each standardized system uses its own carrier frequency or frequencies. A communications apparatus capable of being used in different telecommunications systems must therefore be capable of generating signals oscillating at different carrier frequencies. Now, one and the same synthesizer of little space requirement cannot produce the different carrier frequencies required to work in the different telecommunications systems. Such a synthesizer is said to have limited spectral agility because it cannot produce a signal oscillating at frequencies stretching over a range of several gigahertz. It is therefore necessary to use several distinct synthesizers in the same telecommunications apparatus. Each distinct synthesizer is configured to generate frequencies on a predetermined range different from those generated by the other synthesizers.
The following are also known from the prior art:    Sergei Urazhdin et al, “Fractional synchronization of spin-torque nano-oscillator”, Physical Review Letters, vol. 105, n° 10, Aug. 1, 2010,    B. Georges et al, “Coupling efficiency for phase locking of a spin transfer nano-oscillator to a microwave current”, Physical Review Letters, vol. 101, n° 1, Jan. 7, 2008,    W. Rippard et al, “Injection locking and phase control of spin transfer nano-oscillators”, Physical Review Letters, vol. 95, n° 6, Jan. 8, 2005,    Zarudniev M et al, “Spin torque oscillator characteristics in coupled networks”, Hardware and software implementation and control of distributed mems (DMEMS), 2010, First Workshop on, IEEE, Piscataway, N.J., USA, Jun. 28, 2010, pages 20-23,    US2011/051481A1.
The invention seeks to overcome at least one of these drawbacks.